Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-70-78
E. N. Avdeenko, E. I. Zamulaeva, A. Zaitsev, I. Konyashin, E. Levashov
The structure and properties of coarse-grained WC-6%Co hard metals with carbon deficiency from 0,11 to 1,31 % obtained from narrow fraction tungsten carbide powder with a grain size of 5 to 15 pm were studied with respect to the stoichiometric ratio. According to the results of metallographic analysis, 1390 to 1420 °C sintering temperatures provide a non-porous alloy state with normal carbon content, while alloys with lower carbon content feature considerable porosity. It is found that hard metals with less than 0,02 % residual porosity can be obtained at sintering temperatures of 1450-1475 ° С regardless of the carbon content. It is shown that alloys with 0,11—0,91 % carbon deficiency have a two-phase structure, while the alloy with 1,31 % carbon deficiency contains n phase inclusions in addition to WC and γ phase. It is determined that lower carbon content slows down the tungsten carbide grain growth process during liquid-phase sintering. EDX analysis was used to determine the concentration of tungsten dissolved in the binder phase — 10, 12, 15 and 19 wt.% for hard metals with normal, low, medium and high carbon deficiency, respectively. Narrow fraction WC powders allow obtaining hard metals with rounded grains having a form factor of about 0,77. The alloy with 0,91 % carbon deficiency with respect to the stoichiometric ratio had the best combination of hardness and toughness (11,1 GPa and 16,0 MPa-m 1/2 ).
{"title":"Structure and properties of coarse-grained WC-Со hard metals with extra homogeneous microstructure","authors":"E. N. Avdeenko, E. I. Zamulaeva, A. Zaitsev, I. Konyashin, E. Levashov","doi":"10.17073/0021-3438-2019-4-70-78","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-70-78","url":null,"abstract":"The structure and properties of coarse-grained WC-6%Co hard metals with carbon deficiency from 0,11 to 1,31 % obtained from narrow fraction tungsten carbide powder with a grain size of 5 to 15 pm were studied with respect to the stoichiometric ratio. According to the results of metallographic analysis, 1390 to 1420 °C sintering temperatures provide a non-porous alloy state with normal carbon content, while alloys with lower carbon content feature considerable porosity. It is found that hard metals with less than 0,02 % residual porosity can be obtained at sintering temperatures of 1450-1475 ° С regardless of the carbon content. It is shown that alloys with 0,11—0,91 % carbon deficiency have a two-phase structure, while the alloy with 1,31 % carbon deficiency contains n phase inclusions in addition to WC and γ phase. It is determined that lower carbon content slows down the tungsten carbide grain growth process during liquid-phase sintering. EDX analysis was used to determine the concentration of tungsten dissolved in the binder phase — 10, 12, 15 and 19 wt.% for hard metals with normal, low, medium and high carbon deficiency, respectively. Narrow fraction WC powders allow obtaining hard metals with rounded grains having a form factor of about 0,77. The alloy with 0,91 % carbon deficiency with respect to the stoichiometric ratio had the best combination of hardness and toughness (11,1 GPa and 16,0 MPa-m 1/2 ).","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77388889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-48-56
K. V. Ivanov, E. Glazkova, S. Fortuna, T. Kalashnikova
{"title":"Thermal stability of Al—0,05 vo1.% Al2O3 nanocomposite fabricated by accumulative roll bonding","authors":"K. V. Ivanov, E. Glazkova, S. Fortuna, T. Kalashnikova","doi":"10.17073/0021-3438-2019-4-48-56","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-48-56","url":null,"abstract":"","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91070322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-16-22
A. Zalazinskii, A. Nesterenko, I. Berezin
{"title":"Study of the process of titanium-containing furnace charging material compaction by an experimental-analytical method","authors":"A. Zalazinskii, A. Nesterenko, I. Berezin","doi":"10.17073/0021-3438-2019-4-16-22","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-16-22","url":null,"abstract":"","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91553591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-23-29
B. Bobryshev, V. Moiseev, I. A. Kipin, I. A. Petrov
A factor exerting a decisive influence on the complex of mechanical, technological and operational properties when making castings of magnesium alloys with a wide crystallization range is the casting structure. It is impossible to obtain a required structure of Mg— Al—Zn alloys without melt modification in the melting process. The paper provides the results obtained when studying the process of ML5 magnesium alloy modification with various substances. The influence of 0,4—0,45 wt.% magnesite introduced in the melt at a temperature of 720—740 °C was studied, as well as the influence of melt purging with oxygen-free carboniferous gases at the same temperature on the structure of the obtained alloy and the time of modification effect retention. The latter is especially important in large-lot and mass production of small Mg—Al—Zn—Mn alloy castings for a long time when melt pouring into molds takes considerable time. It is shown that oxygen-free carboniferous gases used for ML5 alloy modification ensure mechanical properties of castings 15 — 20 % higher than the standard level according to GOST 2856-79. The efficiency of retaining the effect of modification using the standard method (magnesite) and with oxygen-free carboniferous gases is compared. It is shown that the effect of modification with magnesite remains within no more than 30—40 minutes, while the effect of modification with oxygen-free carboniferous gas remains not less than 4 hours that enables long pouring of alloy into molds.
{"title":"ML5 alloy structure and properties at different modification methods","authors":"B. Bobryshev, V. Moiseev, I. A. Kipin, I. A. Petrov","doi":"10.17073/0021-3438-2019-4-23-29","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-23-29","url":null,"abstract":"A factor exerting a decisive influence on the complex of mechanical, technological and operational properties when making castings of magnesium alloys with a wide crystallization range is the casting structure. It is impossible to obtain a required structure of Mg— Al—Zn alloys without melt modification in the melting process. The paper provides the results obtained when studying the process of ML5 magnesium alloy modification with various substances. The influence of 0,4—0,45 wt.% magnesite introduced in the melt at a temperature of 720—740 °C was studied, as well as the influence of melt purging with oxygen-free carboniferous gases at the same temperature on the structure of the obtained alloy and the time of modification effect retention. The latter is especially important in large-lot and mass production of small Mg—Al—Zn—Mn alloy castings for a long time when melt pouring into molds takes considerable time. It is shown that oxygen-free carboniferous gases used for ML5 alloy modification ensure mechanical properties of castings 15 — 20 % higher than the standard level according to GOST 2856-79. The efficiency of retaining the effect of modification using the standard method (magnesite) and with oxygen-free carboniferous gases is compared. It is shown that the effect of modification with magnesite remains within no more than 30—40 minutes, while the effect of modification with oxygen-free carboniferous gas remains not less than 4 hours that enables long pouring of alloy into molds.","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73289320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-4-15
M. P. Kuz’min, L. M. Larionov, V. Kondratiev, M. Kuz’mina, V. Grigoriev, А. V. Knizhnik, A. S. Kuz’mina
The paper presents a review of existing methods to produce silumins. The possibility of obtaining foundry alloys using amorphous microsilica is shown. Different methods of adding SiO 2 particles into molten aluminum are studied: in the form of aluminum powder — SiO 2 master alloy tablets, particle mixing in the melt at the liquidus temperature and introducing SiO 2 together with a stream of argon. The paper provides calculations of Gibbs energy formation and change enthalpy for silicon reduction by aluminum from its oxide. Calculations demonstrated the thermodynamic possibility of silumin production using amorphous microsilica. The effect of alloying additives and impurities on the silicon reduction behavior is determined. It is found that magnesium can be used as a surface-active additive to remove oxygen from dispersed particle surfaces and reduce silicon from its oxide. It is determined that the method of aluminum-silicon alloy production by introducing amorphous microsilica preheated to 300 °С into the aluminum melt (t = = 900 °С) together with argon stream (with subsequent intensive mixing) features higher efficiency since it ensures producing aluminum-silicon alloys containing more than 6 wt.% of silicon and microstructure of pre-eutectic foundry silumins. Industrial application of the proposed method will improve the efficiency of the existing silumin production process due to savings on purchasing commercial crystalline silicon. Moreover, this technology will minimize the environmental impact by reducing the volume and subsequent eliminating sludge fields used as landfills for storing dust from silicon gas treatment systems containing up to 95 wt.% of amorphous microsilica.
{"title":"Production of silumins using silicon production waste","authors":"M. P. Kuz’min, L. M. Larionov, V. Kondratiev, M. Kuz’mina, V. Grigoriev, А. V. Knizhnik, A. S. Kuz’mina","doi":"10.17073/0021-3438-2019-4-4-15","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-4-15","url":null,"abstract":"The paper presents a review of existing methods to produce silumins. The possibility of obtaining foundry alloys using amorphous microsilica is shown. Different methods of adding SiO 2 particles into molten aluminum are studied: in the form of aluminum powder — SiO 2 master alloy tablets, particle mixing in the melt at the liquidus temperature and introducing SiO 2 together with a stream of argon. The paper provides calculations of Gibbs energy formation and change enthalpy for silicon reduction by aluminum from its oxide. Calculations demonstrated the thermodynamic possibility of silumin production using amorphous microsilica. The effect of alloying additives and impurities on the silicon reduction behavior is determined. It is found that magnesium can be used as a surface-active additive to remove oxygen from dispersed particle surfaces and reduce silicon from its oxide. It is determined that the method of aluminum-silicon alloy production by introducing amorphous microsilica preheated to 300 °С into the aluminum melt (t = = 900 °С) together with argon stream (with subsequent intensive mixing) features higher efficiency since it ensures producing aluminum-silicon alloys containing more than 6 wt.% of silicon and microstructure of pre-eutectic foundry silumins. Industrial application of the proposed method will improve the efficiency of the existing silumin production process due to savings on purchasing commercial crystalline silicon. Moreover, this technology will minimize the environmental impact by reducing the volume and subsequent eliminating sludge fields used as landfills for storing dust from silicon gas treatment systems containing up to 95 wt.% of amorphous microsilica.","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85075065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-15DOI: 10.17073/0021-3438-2019-4-30-39
S. I. Bogodukhov, E. Kozik, E. V. Svidenko
High-temperature (t = 800 ° С ) ion nitriding of T15K6 indexable carbide inserts was carried out with regard to the structure formation, phase composition, surface coating thickness ensuring an increase in their durability during the cutting test. It was found that hardness and microhardness values increase to 15 % after ion nitriding, however, with a temperature increase of more than 600 °C they gradually decrease to their initial values. Flexural strength after ion nitriding increases by 27 %. The fractography of fractures in the T15K6 carbide surface layers after ion nitriding for 1 and 2 hours at different temperatures showed a very branched fracture structure on edges with a fragile pattern inside the material. The analysis of T15K6 carbide surface layer microstructures after ion nitriding showed that as the ion nitriding temperature increases, the size of conglomerate carbides in the surface layer decreases. The depth of the T15K6 nitrided layer is 1 to 7 pm. Certain regularities of the effect of various ion nitriding time and temperature conditions on the performance characteristics of products made of TK group titanium-tungsten alloys are determined. At 600, 700, 800 °C ion nitriding temperatures and 1 to 8 hours isothermal exposure time, the increase in hardness, microhardness and tensile strength with lower wear was found when cutting T15K6 indexable carbide inserts. It is determined that as the ion nitriding time increases, intergranular destruction areas expand, while the intragranular areas shrink. In case of ion nitriding, a solid solution (Ti x W x )(C 1_y N y ) and (Co 1_x W x )(C 1_y N y ) supersaturated with tungsten is formed and three and four component compounds are released in the surface layer.
{"title":"High-temperature ion nitriding of T15K6 indexable carbide inserts","authors":"S. I. Bogodukhov, E. Kozik, E. V. Svidenko","doi":"10.17073/0021-3438-2019-4-30-39","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-30-39","url":null,"abstract":"High-temperature (t = 800 ° С ) ion nitriding of T15K6 indexable carbide inserts was carried out with regard to the structure formation, phase composition, surface coating thickness ensuring an increase in their durability during the cutting test. It was found that hardness and microhardness values increase to 15 % after ion nitriding, however, with a temperature increase of more than 600 °C they gradually decrease to their initial values. Flexural strength after ion nitriding increases by 27 %. The fractography of fractures in the T15K6 carbide surface layers after ion nitriding for 1 and 2 hours at different temperatures showed a very branched fracture structure on edges with a fragile pattern inside the material. The analysis of T15K6 carbide surface layer microstructures after ion nitriding showed that as the ion nitriding temperature increases, the size of conglomerate carbides in the surface layer decreases. The depth of the T15K6 nitrided layer is 1 to 7 pm. Certain regularities of the effect of various ion nitriding time and temperature conditions on the performance characteristics of products made of TK group titanium-tungsten alloys are determined. At 600, 700, 800 °C ion nitriding temperatures and 1 to 8 hours isothermal exposure time, the increase in hardness, microhardness and tensile strength with lower wear was found when cutting T15K6 indexable carbide inserts. It is determined that as the ion nitriding time increases, intergranular destruction areas expand, while the intragranular areas shrink. In case of ion nitriding, a solid solution (Ti x W x )(C 1_y N y ) and (Co 1_x W x )(C 1_y N y ) supersaturated with tungsten is formed and three and four component compounds are released in the surface layer.","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89602557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-14DOI: 10.17073/0021-3438-2019-4-40-47
G. Tkachuk, V. Maltsev, O. Chikova
The study covers the microstructure and mechanical properties in submicrovolumes of LS59-1A lead brass. Scanning electron microscopy (EDS) was used for metallographic analysis of the studied sample microstructures. It was found that the LS 59-1A brass microstructure along with the main phases ( α phase — solid solution of alloying elements in copper and β phase — solid solution based on the CuZn electronic compound) also contains globular inclusions of free lead (1—2 vol.%) localized on grain boundaries and in interdendritic regions. In addition, exogenous nonmetallic inclusions of CuO + ZnO and pores were found in the microstructure. Oxide inclusions and compounds containing iron and manganese are localized at the boundaries of α and β phases. A nanoindentation method was used to study hardness ( Н ) and Young’ modulus of α and β phases. An insignificant difference was found between H values for a phase dendrites with respect to the β phase interdendritic space indicating higher homogeneity of LS59-1A ingot mechanical properties. Calculation of additional pressure that occurs at the interface of a and β phases when external force is applied to the material due to a difference in Young’s moduli showed that it is 23 times higher than external force, which can cause destruction of LS59-1A brass ingots during machining. The results obtained are discussed from the standpoint of modern ideas about the metallographic method used to control brass ingot quality under industrial production conditions.
{"title":"Research of microstructure and mechanical properties in LS59-1A brass submicrovolumes","authors":"G. Tkachuk, V. Maltsev, O. Chikova","doi":"10.17073/0021-3438-2019-4-40-47","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-4-40-47","url":null,"abstract":"The study covers the microstructure and mechanical properties in submicrovolumes of LS59-1A lead brass. Scanning electron microscopy (EDS) was used for metallographic analysis of the studied sample microstructures. It was found that the LS 59-1A brass microstructure along with the main phases ( α phase — solid solution of alloying elements in copper and β phase — solid solution based on the CuZn electronic compound) also contains globular inclusions of free lead (1—2 vol.%) localized on grain boundaries and in interdendritic regions. In addition, exogenous nonmetallic inclusions of CuO + ZnO and pores were found in the microstructure. Oxide inclusions and compounds containing iron and manganese are localized at the boundaries of α and β phases. A nanoindentation method was used to study hardness ( Н ) and Young’ modulus of α and β phases. An insignificant difference was found between H values for a phase dendrites with respect to the β phase interdendritic space indicating higher homogeneity of LS59-1A ingot mechanical properties. Calculation of additional pressure that occurs at the interface of a and β phases when external force is applied to the material due to a difference in Young’s moduli showed that it is 23 times higher than external force, which can cause destruction of LS59-1A brass ingots during machining. The results obtained are discussed from the standpoint of modern ideas about the metallographic method used to control brass ingot quality under industrial production conditions.","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82318730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-19DOI: 10.17073/0021-3438-2019-3-36-46
Y. Pogozhev, M. Lemesheva, A. Potanin, S. Rupasov, V. Vershinnikov, E. Levashov
The paper focuses on obtaining heterophase powder ceramics and consolidated ceramics based on borides and silicides of hafnium and molybdenum by combining the methods of self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic SHS powders HfB2–HfSi2–MoSi2 were obtained according to the scheme of magnesium-thermal reduction from oxide raw materials where the combustion wave is characterized by temperatures of 1750–2119 K and high mass combustion rates of 8,4– 9,3 g/s. The structure of synthesized SHS powders consists of relatively large MoSi2 grains up to 10 μm in size and submicron elongated HfB2 grains located mainly inside the MoSi2 grains and rounded Si precipitates. The composition with a lower concentration of boron contains a large number of polyhedral HfSi2 grains with a size of less than 10 μm. The resulting powders are characterized by an average particle size of ~6 μm with a maximum size up to 26 μm. Phase compositions of ceramics consolidated by the HP method and SHS synthesized powders are identical. The microstructure of compact samples consists of faceted HfB2 elongated grains 0,5– 10,0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size and silicon interlayers. Consolidated ceramics has a high structural and chemical homogeneity, low residual porosity of 1,1–1,7 %, high hardness of 11,7–12,6 GPa and thermal conductivity of 62–87 W/(m·K).
{"title":"Heterophase ceramics in the Hf–Si–Mo–B system obtained by a combination of SHS and hot pressing methods","authors":"Y. Pogozhev, M. Lemesheva, A. Potanin, S. Rupasov, V. Vershinnikov, E. Levashov","doi":"10.17073/0021-3438-2019-3-36-46","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-3-36-46","url":null,"abstract":"The paper focuses on obtaining heterophase powder ceramics and consolidated ceramics based on borides and silicides of hafnium and molybdenum by combining the methods of self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic SHS powders HfB2–HfSi2–MoSi2 were obtained according to the scheme of magnesium-thermal reduction from oxide raw materials where the combustion wave is characterized by temperatures of 1750–2119 K and high mass combustion rates of 8,4– 9,3 g/s. The structure of synthesized SHS powders consists of relatively large MoSi2 grains up to 10 μm in size and submicron elongated HfB2 grains located mainly inside the MoSi2 grains and rounded Si precipitates. The composition with a lower concentration of boron contains a large number of polyhedral HfSi2 grains with a size of less than 10 μm. The resulting powders are characterized by an average particle size of ~6 μm with a maximum size up to 26 μm. Phase compositions of ceramics consolidated by the HP method and SHS synthesized powders are identical. The microstructure of compact samples consists of faceted HfB2 elongated grains 0,5– 10,0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size and silicon interlayers. Consolidated ceramics has a high structural and chemical homogeneity, low residual porosity of 1,1–1,7 %, high hardness of 11,7–12,6 GPa and thermal conductivity of 62–87 W/(m·K).","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"192 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91444104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-19DOI: 10.17073/0021-3438-2019-3-20-29
A. Kataev, O. Tkacheva, N. Molchanova, Y. Zaikov
The study covers the process of obtaining the Al–B master alloy by the KBF4and B2O3aluminothermic reduction using KF–AlF3and KF–NaF–AlF3fluoride fluxes at 983 and 1123 К, respectively, and KCl–NaCl–KF chloride-fluoride fluxes at Т= 1173÷1223 К. All experiments were carried out under the same conditions: molten mixture stirring rate was 400 rpm, synthesis duration was 30min. The maximum amount of boron (1,5 %) in the Al–B alloy was obtained when using KBF4(3 % per B) as a boron-containing raw material in the KF–AlF3medium with a molar (cryolite) ratio (CR) of KF/AlF3equal to 1,3, atТ= 983 К, while boron recovery ratio did not exceed 75 %. Comparable results were obtained in experiments with KF–NaF–AlF3f lux (CR = 1,5) at Т= 1123 К. However, with the increased concentration of fed boron its recovery ratio decreased substantially. It is connected with the higher decomposition temperature of not only KBF4, but also less thermally stable NaBF4 formed as a result of exchange reaction in the melt. Therefore it is not recommended to use sodium salts as a f lux component. The Al–B master alloys obtained by KBF4reduction in fluoride fluxes were solid solutions of B in Al containing the AlB2intermetallic compound. The lowest amount of boron in aluminum with the minimum degree of extraction was obtained in experiments with the B2O3in molten KF–AlF3with CR = 1,5. Nevertheless, the results of scanning electron microscopy indicate a uniform distribution of B over the Al matrix and the absence of intermetallic compounds, while a large amount of Al2O3was found, which is the product of B2O3reactions with both liquid Al and KF–AlF3flux.
{"title":"Production of the Al–B master alloy by KBF4and B 2O3aluminothermic reduction in molten salt flux medium","authors":"A. Kataev, O. Tkacheva, N. Molchanova, Y. Zaikov","doi":"10.17073/0021-3438-2019-3-20-29","DOIUrl":"https://doi.org/10.17073/0021-3438-2019-3-20-29","url":null,"abstract":"The study covers the process of obtaining the Al–B master alloy by the KBF4and B2O3aluminothermic reduction using KF–AlF3and KF–NaF–AlF3fluoride fluxes at 983 and 1123 К, respectively, and KCl–NaCl–KF chloride-fluoride fluxes at Т= 1173÷1223 К. All experiments were carried out under the same conditions: molten mixture stirring rate was 400 rpm, synthesis duration was 30min. The maximum amount of boron (1,5 %) in the Al–B alloy was obtained when using KBF4(3 % per B) as a boron-containing raw material in the KF–AlF3medium with a molar (cryolite) ratio (CR) of KF/AlF3equal to 1,3, atТ= 983 К, while boron recovery ratio did not exceed 75 %. Comparable results were obtained in experiments with KF–NaF–AlF3f lux (CR = 1,5) at Т= 1123 К. However, with the increased concentration of fed boron its recovery ratio decreased substantially. It is connected with the higher decomposition temperature of not only KBF4, but also less thermally stable NaBF4 formed as a result of exchange reaction in the melt. Therefore it is not recommended to use sodium salts as a f lux component. The Al–B master alloys obtained by KBF4reduction in fluoride fluxes were solid solutions of B in Al containing the AlB2intermetallic compound. The lowest amount of boron in aluminum with the minimum degree of extraction was obtained in experiments with the B2O3in molten KF–AlF3with CR = 1,5. Nevertheless, the results of scanning electron microscopy indicate a uniform distribution of B over the Al matrix and the absence of intermetallic compounds, while a large amount of Al2O3was found, which is the product of B2O3reactions with both liquid Al and KF–AlF3flux.","PeriodicalId":14523,"journal":{"name":"Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74461985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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